According to the BBC, on 4/3/04 Spanish authorities found a bomb attached to a rail in Madrid. The bomb was found to be of the same make and type of the bombs used on 3/11/04.

"Bomb disposal experts found between 10 and 12kg (22-24lb) of explosives, which were connected to a detonator with a 135m cable."
http://news.bbc.co.uk/1/hi/world/europe/3596455.stm

The bomb was also the same weight as the bombs used on the trains.

"All four trains had passed through Alcala de Henares station on their way to the Atocha terminus in the city centre. As each one stopped, the bombers loaded bags packed with about 10kg of explosives onboard."
http://news.bbc.co.uk/1/shared/spl/hi/europe/05/madrid_bombings/html/1.stm

So what kind of damage does 23 lbs.(10-12kg.) of high explosives do? Look at the Madrid train in the picture above.

Do the two look similar? The Madrid train looks worse. Still, you'd have to say that the London train was hit by at least half of what hit the Madrid train. Say 10 lbs, for the sake of argument. 10 pounds of "High Explosives". The AP reported on the London bombs:

"...the forensic investigation suggests that each device used had less than 10 pounds of high explosives,'' Hayman said. The weight of explosives was smaller than recent bombs detonated in the Middle East.
http://www.officer.com/article/article.jsp?siteSection=1&id=24635

"...less than 10 pounds...". So, I'm SOLD on the idea that the explosives used in London were High Explosives of a higher end commercial grade (as in Madrid), if not military.

We all know that the authorities in Britain and elsewhere first described the explosives as military or high grade. Then, all of a sudden the story changed to "homemade" bombs. Bombs assembled from drugstore bought materials.

"The suicide bombers cooked up their explosives using mundane items like hydrogen peroxide. They stored them in a fancy commercial refrigerator that was out of place in their grimy flat. And cell phones likely were used to set them off."
-AP
http://www.freerepublic.com/focus/f-news/1456500/posts

"The bombs used, all under 10 lbs, were likely to have been carried in rucksacks.
Explosives expert Andy Oppenheimer, of Jane's Information Group, said: "These could have been home-made devices, they would not have been difficult to make.”
-YNET
http://www.ynetnews.com/Ext/Comp/ArticleLayout/CdaArticlePrintPreview/1,2506,L-3110182,00.html

I will safely assume that military and commercial grade explosives are more powerful than anything that can be assembled from scratch. To match the intensity of a military or commercial explosive (pound for pound), you would have to have many MORE lbs. worth of the homemade explosive. I mean, I don't have the stats on that, but it stands to reason.

No one has retracted the weight of the bombs used on 7/7. They only changed it's quality.

But there lies the problem with all this. "Less than 10 pounds" of "Homemade material" could NOT have done the damage in London. Maybe 12 or 14 pounds of High Explosives, but not the stuff you make with fingernail polish and beeswax, or whatever they supposedly used.